SwingWorker Example

Here's a basic example of how to use a SwingWorker for a long running background task.

Idle

Running

<geshi lang="java5"> package swingworker;

import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.FlowLayout; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Random;

import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField; import javax.swing.SwingUtilities; import javax.swing.WindowConstants;

import org.jdesktop.swingworker.SwingWorker;

public class LuckyNumber extends JFrame implements ActionListener { private static final long serialVersionUID = 4276832367310733568L; private JLabel label; private JButton cancel; private JButton start; private SwingWorker<?,?> worker; private JTextField textField;

public LuckyNumber() { JPanel panel = new JPanel(); panel.setLayout(new GridLayout(2, 1));

JPanel buttons = new JPanel(new FlowLayout()); start = new JButton("Start"); start.addActionListener(this); start.setDefaultCapable(true); buttons.add(start); cancel = new JButton("Cancel"); cancel.setEnabled(false); cancel.addActionListener(this); buttons.add(cancel); panel.add(buttons);

ImageIcon image; if (getClass().getResourceAsStream("/swingworker/spinner.gif") != null) image = new ImageIcon("swingworker/spinner.gif"); else image = new ImageIcon("");

label = new JLabel(image); JPanel answer = new JPanel(new GridLayout(1, 2)); textField = new JTextField(""); answer.add(textField); answer.add(label); label.setVisible(false); panel.add(answer);

setTitle("Lucky number generator"); setPreferredSize(new Dimension(300, 100)); getContentPane().setLayout(new BorderLayout()); getContentPane().add(panel);

}

public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { LuckyNumber luckyNumber = new LuckyNumber(); luckyNumber.pack(); luckyNumber.setVisible(true); luckyNumber.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); } }); }

public void actionPerformed(ActionEvent e) { if (e.getSource() == start) { start.setEnabled(false); textField.setText(""); worker = new NumberWorker(); worker.execute(); label.setVisible(true); cancel.setEnabled(true); } else if (e.getSource() == cancel) { cancel(); }

}

@Override public void dispose() { cancel(); super.dispose(); }

private void cancel() { start.setEnabled(true); label.setVisible(false); cancel.setEnabled(false); if (worker != null) { worker.cancel(true); worker = null; }

}

private class NumberWorker extends SwingWorker<String, Object> {

private Random r = new Random();

@Override protected String doInBackground() throws Exception { long s = System.currentTimeMillis(); while (System.currentTimeMillis() - s < 5000 && !Thread.currentThread().isInterrupted()) { r.nextInt(); } return String.valueOf(r.nextInt(10) + 1); }

@Override protected void done() { try { textField.setText(get()); LuckyNumber.this.worker = null; LuckyNumber.this.cancel(); } catch (Exception ignore) { } } }

} </geshi>